Officials investigating captured Bosnian Serb ex-leader Radovan Karadzic say they will track down and punish those who aided his false identity.
Serb prosecutors believe he held the identity of Dragan Dabic for a long time thanks to papers issued under the regime of President Slobodan Milosevic.
A spokesman said those who helped Mr Karadzic knew they were committing a criminal act and would be prosecuted.
The war crimes tribunal in The Hague is pushing for Mr Karadzic's extradition.
Mr Karadzic was captured on Monday after more than a decade in hiding.
'Parallel life'
Bruno Vekaric, a spokesman for Serbia's war crimes prosecutor, said Mr Karadzic clearly obtained his papers from his "friends" in the Milosevic regime, which fell in 2000.
The fake ID was issued in Ruma, a town north of Belgrade, possibly with the help of Slobodan Medic, a now-captured local paramilitary commander, Mr Vekaric said.
He said officials were trying to determine the true identity of Dragan Dabic but as there were a number of people with that name he would not speculate further.
Some reports suggest Dabic was a slain Serb fighter, others that he was a civilian killed in Bosnia's capital during the war.
Mr Vekaric said only a few people were aware of Mr Karadzic's use of the Dabic name and that they would all have to answer to prosecutors.
Mr Vekaric said he hoped these people would provide information leading to the capture of the remaining war crimes fugitives, including Bosnian Serb military leader Gen Ratko Mladic.
"Whoever was helping Karadzic was committing a criminal act, and they know it," Mr Vekaric said.
He told the daily Vecernje Novosti that Mr Karadzic "started living his parallel life much earlier" than Gen Mladic.
'Step forward'
Mr Karadzic's life on the run still dominates Serbian media.
He masqueraded as an expert in human quantum energy, had his own website and gave out business cards during alternative medicine lectures.
Some newspapers on Thursday printed photographs which they said were of his girlfriend, a woman in her 40s they called Mila.
Posters appeared briefly in the eastern Bosnian town of Visegrad declaring "We are with you, President" before police removed them.
Mr Karadzic, who has now had a shave and haircut in custody, intends to conduct his own defence in The Hague once extradited.
His lawyer, Sveta Vujacic, says he will appeal against the extradition - but not until just before Friday's deadline, and that the document will be posted instead of being hand delivered.
Correspondents say this is a delaying tactic and that it is almost inevitable that Mr Karadzic will be extradited.
There is speculation that, like Milosevic, Mr Karadzic intends to drag proceedings out for as long as possible - possibly until 2010, when the court's United Nations mandate runs out.
US Secretary of State Condoleezza Rice said his arrest showed Serbs were "making a step forward in closing an ugly chapter in their past, and I just hope that Mladic is next".
Mr Karadzic, 63, declared independence for Bosnian Serbs in 1991, sparking the 1992-1995 Bosnian war.
He has been indicted for crimes against humanity and genocide over the massacre of up to 8,000 mainly-Muslim Bosniaks at Srebrenica in 1995.
He has also been charged over the shelling of Sarajevo, and the use of 284 UN peacekeepers as human shields in May and June 1995.
PHOTO CAPTION:
Some Serbs have come out in support of the captured Karadzic
BBC